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Underground Astronomy II

StarDate:

March 2, 2011

Something is always interfering with the view of the heavens. For most telescopes, it's clouds or moonlight. But for some other instruments, it's cosmic rays or the radioactivity in the rocks and soil.

For those instruments, the solution is to bury them under thousands of feet of water, ice, or rock -- something that's happening in laboratories all across the world. Astronomers have placed their instruments beneath the ice at the South Pole, beneath the waters of the Mediterranean Sea, and deep in gold, zinc, and nickel mines.

These deep locations filter out the cosmic rays, which are energetic particles from far beyond Earth. But some of the locations produce their own radiation, from the radioactive decay of the rocks around them. And for some experiments, even a tiny bit of radiation is too much.

Consider the Enriched Xenon Observatory, which is designed to study neutrinos. It requires an extraordinarily radiation-free environment. So the observatory was built of special materials, assembled in clean rooms, encased in lead, then sealed inside a 30-ton concrete hull. It was shipped by truck to avoid the exposure to cosmic rays that air travel brings. Then it was installed a half-mile down in a salt mine in New Mexico, because salt has lower levels of radioactivity than most other rock beds. And all of that just to study some of the most elusive particles in the universe.

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